juice

In normal usage, juice refers to fruit juice, but there are also vegetable juices.

Fruit juices are very popular: They are sweet; they are mixes of several types of fruit or mixed with water; they are refreshing and healthy; and the wide range of different domestic and exotic fruits and combinations bring variety to our diet.

Not all juices are alike, however: The proportion of naturally occurring and added sugar, the existing vitamins, and above all the types of drinks containing fruit juice determine the true health benefit. The regulations concerning fruit juice stipulate exactly when a drink may or may not be called fruit juice, fruit nectar or fruit juice drink. As part of a healthy diet, undiluted juices and sweetened drinks should not be drunk to quench one’s thirst. After all, a 250-ml glass of apple juice contains about 30 g of sugar, equivalent to 10 sugar cubes, which – at easily 140 kcal – constitutes quite a large amount of the recommended daily allowance.

The various types of juice, their methods of production and their nutritional importance are explained below.

Definitions

* Fruit juice Fruit juice consists of 100% juice. It is pressed out or extracted from the fruits, whereby juice extract is processed almost exclusively as concentrate. (More information can be found below under ‘Production’.) One or more types of fruit may be used to this end. Pulp and pulp cells that are separated from the juice during processing may be added again. Following extraction, the juice is filtered at most and very briefly pasteurised to prevent fermentation before it is bottled. The aroma, flavour and true colour typical for the fruit or fruits must be preserved. To offset a naturally sour taste, at most 15 g of sugar per litre may be added; to obtain a sweet flavour 150 g per litre are allowed. In every case the addition of sugar must be shown on the label. Citric acid may be added to improve the sour components. The simultaneous addition of sugar and citric acid is not allowed, however. Water, artificial colours and preservatives may not be added.

* Fruit juice concentrate or concentrated fruit juice Fruit juice concentrate is fruit juice from which the water has been removed. In order to minimize loss through spoilage and to save on the costs of production and transportation, fruits are processed into juice in the country of origin. Concentration reduces the volume, enabling more of the product to be transported per load.

* Fruit juice from fruit juice concentrate If the water that was removed in concentration and aromas and pulp that may have been lost are added again to fruit juice concentrate (see above), the product is known as fruit juice from fruit juice concentrate. This product must smell and taste and have the same analytical characteristics as the original juice.

* Fruit pulp Straining the edible part of whole or peeled fruits without separating the juice produces fruit pulp, also called fruit purée. It consists of fruit pulp and fruit juice. Because it is produced from the entire fruit, fruit pulp has a higher content of vitamin, minerals, tannins and fibre and often more energy than all other juice-like fruit products.

* Fruit nectar Fruit nectar is produced from fruit pulp by adding water and sugar or honey. Added sugar and honey may account for at the most 20% of the total product. Depending on the kind of fruit, it must contain a minimum of between 25 and 50% fruit juice, for nectars of citrus fruits more than 50%. Nectar contains all insoluble cellular components of the original fruit. Certain types of fruit may be processed as nectar singly or mixed, even without the addition of sugar or honey; among these are apricots, apples, pears, peaches and mangos. Artificial colours, artificial flavours and preservatives may not be added. Fruit nectars are also sold as light or diet products. When we speak of nectar in connection with blossoms or the extraction of honey we are referring to a clear substance containing protein and sugar that is harvested from the nectary, the gland of the plant that secretes nectar.

* Fruit juice drinks These are unsweetened or sweetened refreshment beverages made of fruit juice, fruit juice concentrate, fruit pulp or mixtures thereof and water. They have the lowest required fruit content: for drinks with citrus fruits at least 6%, for those with stone fruits and/or grapes at least 30%, and for all other types of fruit at least 10%. Here as well, preservatives may not be added, but natural aromas are allowed because the very low fruit content is often insufficient to provide a full flavour. Most light and diet juice drinks are fruit juice drinks.

* Fruit syrup Syrup is a viscous solution formed, in this case, by dissolving sugar in fruit juices, fruit juice concentrates or fruits. The mixture may be cooked or not.

* Smoothie Smoothies are a relatively new product and are considered to be very healthy; they are sometimes even advertised as a substitute for fresh fruit. Unfortunately, this is often not true. There is still no legal definition of smoothies, which means that various products can be sold as such. They actually have in common only their thick, smooth consistency. A smoothie is usually a mixture of fruit juice and fruit pulp to which in some cases preparations of pectin or other thickening agents are added to provide the customary smooth consistency. Owing to the lack of legal regulations, aromas and sweeteners may also be added. If these additions are done without, smoothies are, practically speaking, fruit pulp and thus relatively rich in valuable ingredients. They are nonetheless no substitute for fresh fruit: The heating during processing reduces their vitamin content, and the amounts of fibre and secondary plant substances in raw fruit are significantly higher.

* Soft drinks Soft drinks or sodas are refreshment beverages made of water, flavouring preparations and/or natural aromas, and sugar, usually with carbon dioxide, and with edible acids, usually citric acid. Fruit juices and concentrates as well as sweeteners may also be used.

Production

The fruits used to make fruit juice must fulfil certain quality criteria. They should be ripe but not overripe, healthy, not damaged and not spoiled. The contents of aroma, sugar and acidity play an important role, as do, depending on the fruit, the vitamin C or pigment content and the expected juice yield.

1) Extraction of the raw juice Fruit juice is gained by pressing chopped, blanched fruit – the mash. To facilitate the flow of juice and thus obtain a higher yield, the cell walls must first be destroyed. This was achieved earlier by heating, but since many essential ingredients are lost in this way, the cell walls are dissolved enzymatically today. Enzymes are added to the chopped fruit which dissolve out the propectin and thus loosen the tissue. In this way nearly all edible parts of the fruit are made fluid, a further advantage over heating. At the same time pectin is formed and this also serves a function: it stabilizes the sediment in the juice so that single particles cannot settle to the bottom as quickly. This process yields 65–90 litres of juice per 100 kg of fruit. This so-called enzymatic maceration can also be used in the production of fruit pulp and nectar. As an alternative to pressing, juice can be extracted. The chopped fruit is subjected to flowing water, which leaches it out. At 95%, the yield is greater than with pressing. However, the juice is lighter and richer in minerals and tannins. Therefore, it tastes different and is processed almost exclusively to concentrate.

2) PreservationBy means of pasteurisation (heating to just under 100°C for a short period of time) the enzymes responsible for the degradation of colour, aroma and vitamins are destroyed. Moreover, any existing micro-organisms are rendered harmless. An alternative is the addition of ascorbic acid, which serves as an antioxidant. The addition of preservatives for the purpose of conservation is forbidden.

3) Purification and clarification If the product is intended to be a clear juice, the sediment particles and dissolved substances that may later cause turbidity are removed in this step. This is accomplished with filtration, enzymatic degradation, or the addition of substances that bind the sediment and can then be separated out. Purification is also sometimes done to improve the organoleptic, or sensory, characteristics of the juice.

Ingredients

The composition of different types of fruit may vary greatly. For example, citrus fruits differ in structure from berries or apples and contain other compositions of vitamins. Within species and varieties as well (such as the apple) and even within the same variety there may be strong fluctuations. Just as each wine vintage delivers differing products, although the same variety of grape of always used, fruit juices from each individual production series can exhibit differences in their sensory features and contents.

In accordance with the directive regarding fruit juice, some similar products and nectar (the fruit juice directive), with the exception of natural ascorbic acid (vitamin C) and if need be a small amount of sugar or lemon juice, no substances may be added, and thus also no vitamins. If the label contains a reference to the vitamin-C content, then the product must contain at least 20 mg of vitamin C per 100 ml. If the claim is “rich in vitamin C”, it must contain at least 30 mg.

In the processing of fruit to juice drinks ingredients are partially damaged or destroyed, making the products less valuable than the original fruit. Fruit juices and pulps as well as smoothies nevertheless remain good sources of important plant substances. One should not drink too much of them, however, because their energy content is quite high: only one glass (200 ml) of apple juice, for instance, provides just under 100 kcal. This is approximately the same amount as when one eats an apple, but the apple is also filling.

Fruit juices, fruit juices from concentrate, smoothies, fruit pulps and nectars contain appreciably more vitamins and minerals than fruit juice drinks do. Their natural flavour is also more intensive. The fact that fruit juice drinks are also allowed to be sweetened is another argument for drinking fruit juice. In case of doubt, therefore, it is worth it to pay more. Grape juice, pineapple juice and apple juice are particularly high in energy.

The fibre contained in fresh fruits is no longer available in juice and nectar. Some fruit juices contain a large amount of vitamin C, of which adolescents and adults require about 100 mg per day. A good half of this amount is covered by 100 ml of orange or lemon juice, and even more than half is provided by the juice of sea-buckthorn berries.

Fruit juices and nectars are also good suppliers of potassium. Elderberry, sea-buckthorn berry and passion-fruit juice stand out; 100 ml of each provides more than one tenth of our daily requirement.

Unfortunately, vitamins and other substances do not keep as long as the juice itself. If orange juice is stored for 18 months in a cool cellar (16°C), the vitamin-C content is reduced by 16%.

The loss is even greater when the bottle has already been opened. Vitamins, aromatic substances and colours are sensitive to the effect of oxygen, and their content is reduced, the longer the juice has been open. In addition to the loss of vitamins, this results in discolouring and changes in flavour even before the best-by date is reached and before spoilage reactions begin. Therefore, all specifications regarding the vitamin content are always mean values.

Inactivated remains of enzymes added in production do not have to be specifically labelled but sometimes are. The enzymes are used to destroy the cell walls of the fruit. This increases the yield of juice, and the ingredients are preserved. Prior to bottling, the enzymes are inactivated by being heated for a short time or filtered out. For most people the residues are then harmless, but in a small number of allergy sufferers they can trigger reactions.

To avoid the loss of vitamins, colour and aroma, juice products should be stored for only a short time and in a cool, dark environment. After they have been opened, they should be kept in the refrigerator and used up within several days. However, they should not be drunk too cold, as the aromas develop better at warmer temperatures.

With the website www.the-green-pantry.com the Fritz Terfloth Foundation of Münster offers consumers independent and competent information about plant foods and their health effects. All texts are subject to German copyright law. Information about the conditions for use of the texts by third parties can be found here.